Background

Since 1991 to 2008 approximately 800,000 Exeter stems have been sold worldwide with 80 reported cases of fracture (neck or stem). This study aimed to determine factors predisposing to fracture.

Aim

The aim of this study was to determine the medium term survivorship and function of the Exeter Universal Hip Replacement when used in younger patients, a group that is deemed to place high demands on their arthroplasties. Since 1988 The Exeter Hip Research Unit has prospectively gathered data on all patients who have had total hip replacements at the Princess Elizabeth Orthopaedic Hospital. There were 130 Exeter Universal total hip replacements (THR) in 107 patients who were 50 years or younger at the time of surgery and whose surgery was performed at least 10 years before. Mean age at surgery was 42 years (range 17-50 years.) Six patients who had 7 THRs had died, leaving 123 THRs for review. Patients were reviewed at an average of 12.5 years (range 10-17 years). No patient was lost to follow-up.

Purpose

We describe an update of our experience with the implantation of the first 325 Exeter Universal hips. The fate of every implant is known.

Introduction & methods: The aim of this study was to determine the medium term survivorship and function of the Exeter Universal Hip Replacement when used in younger patients, a group that is deemed to place high demands on their arthroplasties. Since 1988, The Exeter Hip Research Unit has prospectively gathered data on all patients who have had total hip replacements at the Princess Elizabeth Orthopaedic Hospital. There were 130 Exeter Universal total hip replacements (THR) in 107 patients who were 50 years or younger at the time of surgery and whose surgery was performed at least 10 years before. Mean age at surgery was 42y (range 17y to 50y.) Six patients who had 7 THRs had died leaving 123 THRs for review. Patients were reviewed at an average of 12.5 years (range 10 – 17 years). No patient was lost to follow up. Results: At review, 12 hips had been revised. Of these, 9 were for aseptic loosening of the acetabular component and one cup was revised for focal lysis and pain. One hip was revised for recurrent dislocation. One femoral component required revision in 1 case of infection. Radiographs showed that a further 11(10%) of the remaining acetabular prostheses were loose but that no femoral components were loose. Survivorship of stem and cup from all causes was 92.7%, at an average of 12.5 years. Survivorship of stem only from all causes was 99% and from aseptic loosening was 100%.

Conclusion: The Exeter Universal Stem is shown to perform extremely well in the younger patient. No femoral component became loose and only 9 acetabular components were revised for aseptic loosening

Introduction: We describe an update of our experience with the implantation of the first 325 Exeter Universal hips. The fate of every implant was known.

Methods: This is a review of the prospective data collected from the first 325 Exeter Universal stems (309 patients) inserted between March 1988 and February 1990. The procedures were undertaken by surgeons of widely differing experience. Clinical and radiological review was performed at a mean of 15.4 years.

Results: At last review 185 patients had died (192 hips). 104 hips remain in-situ. Survivorship at 17 years with revision for femoral component aseptic loosening was 100% (95% CI 97 to 100), with revision for acetabular component aseptic loosening was 92.85% (95% CI 87.0 to 96.2) and with any re-operation as the endpoint was 83.99% (95% CI 77.1 to 90.27). 12 patients (12 hips) were not able to attend for review due to infirmity or emigration, and scores were obtained by phone (x-rays were obtained in 4 patients). Mean D’Aubigné and Postel scores (Charnley modification) at review were 5.4 for pain and 4.5 for function. The mean Oxford score was 21.46 +/− 9.52 and the mean Harris score 73.35 +/− 17.32. On radiological review there were no femoral component failures. Three sockets (2.9%) were loose as demonstrated by migration or change in orientation (two patients were asymptomatic) and 5 sockets (4.8%) had radiolucent lines in all 3 zones but no migration. There are two patients awaiting socket revision.

Discussion: The high rate of clinical and radiological success of the Exeter Universal stem seen at 12 years is sustained at 17 years. Further cup failures have occurred but overall survivorship remains good. With the favourable long-term behaviour of the original Exeter stem, we feel optimistic that good function of the Universal stem will continue through the third decade.

Introduction & Aims: To study the survivorship and subsidence patterns of the first 433 Exeter polished, totally collarless, double tapered, cemented stems that were inserted between November of 1970 and the end of 1975 by 16 different surgeons (13 of them in the training grades) utilising first generation cementing techniques.

Method: A survivorship study up to the 33rd year of follow-up, using the contingency table method, was performed for all 433 hips, the end-point being revision for aseptic stem loosening. Stem subsidence in relation to the cement and the bone was measured in all survivors by a single observer on digitised films (magnified 200%) using the Orthochart™ software. Stem subsidence, the grade of cementing, ‘calcar’ resorption, visible cement fractures, focal lysis and radiolucent lines at the interfaces were assessed.

Results: Of the 433 hips, 21 were revisions of previously failed hips. 21.7% of patients have had a re-operation of some sort including 3.69% for stem fracture, 3.46% for neck fracture (all from a group of 95 stems with excessively machined necks), 9% for aseptic cup loosening, 3.46% for aseptic stem loosening, 1.84% for infection and 0.23% for recurrent dislocation). For the overall series, with revision for aseptic stem loosening as the end-point, the survivorship is 91.42% (95%CI: 70.82 to 100%). When all cases lost to follow-up (28 hips) are regarded as failures, survivorship is 82.9% (95%CI: 58.37 to 100%).

The average age at operation of the survivors was 55.7 years. No significant radiological subsidence between the cement and bone was found. Mean subsidence between the stem and the cement was 2.15mm, most occurring in the first 5 years and in all but 1 being less than 4. The maximum was 18mm (grade D cementing). Cementing grades were B in 65%, C in 27%, D in 8%. Resorption of the neck (13%) was associated with excessive socket wear or cement left over the cut surface of the neck (the ‘pseudocollar’). Visible cement fractures were found in 14%, none associated with focal lysis, which was seen in 11%.

Conclusions: Although 21.7% of patients in this series of the first 433 Exeter hips to be inserted in Exeter needed a re-operation of some sort, the stem rarely required surgery for aseptic loosening and was associated with benign long-term X-Ray appearances in spite of 1st generation cementing.

Introduction and Aims: To study the survivorship and subsidence patterns of the first 433 Exeter polished, totally collarless, double tapered, cemented stems that were inserted between November 1970 and the end of 1975 by 16 different surgeons (13 of them in the training grades) utilising first generation cementing techniques.

Method: A survivorship study up to the 33rd year of follow-up, using the contingency table method, was performed for all 433 hips, the end-point being revision for aseptic stem loosening (including also a ‘worst case’ scenario). Stem subsidence in relation to the cement and the bone was measured in all survivors by a single observer on digitised films (magnified 200%) using the Orthochart™ software. Repeated measurements allowed the analysis of intra-observer errors. Stem subsidence, the grade of cementing, ‘calcar’ resorption, visible cement fractures, focal lysis and radiolucent lines at the interfaces were assessed.

Results: Of the 433 hips, 21 were revisions of previously failed hips. 21.7% of patients have had a re-operation of some sort, including 3.69% for stem fracture, 3.46% for neck fracture (all from a group of 95 stems with excessively machined necks), 9% for aseptic cup loosening, 3.46% for aseptic stem loosening, 1.84% for infection and 0.23% for recurrent dislocation). For the overall series, with revision for aseptic stem loosening as the end-point, the survivorship is 91.42% (95%CI: 70.82 to 100%). When all cases lost to follow-up (28 hips) are regarded as failures, survivorship is 82.9% (95%CI: 58.37 to 100%).

The average age at operation of the survivors was 57.6 years. No significant radiological subsidence between the cement and bone was found. Mean subsidence between the stem and the cement was 2.15mm, most occurring in the first five years and in all but one being less than four. The maximum was 18mm (grade D cementing). Cementing grades were B in 65%, C in 27%, D in 8%. Resorption of the neck (13%) was associated with excessive socket wear or cement left over the cut surface of the neck (the ‘pseudocollar’). Visible cement fractures were found in 14%, none associated with focal lysis, which was seen in 11%.

Conclusion: Although 21.7% of patients in this series of the first 433 Exeter hips to be inserted in Exeter needed a re-operation of some sort, the stem rarely required surgery for aseptic loosening and was associated with benign long-term x-ray appearances in spite of 1st generation cementing.

Introduction and aims: To study the survivorship and subsidence patterns of the first 433 Exeter stems inserted between 1970 and 1975 by 16 different surgeons utilising first generation cementing techniques.

Method: A survivorship study up to the 33rd year of follow-up was performed, the end-point being revision for aseptic stem loosening. Stem subsidence was measured in all survivors, as well as assessing the grade of cementing, ‘calcar’ resorption, visible cement fractures, focal lysis and radiolucent lines at the interfaces.

Results: Of the 433 hips, 21 were revisions of previously failed hips. 21.7% of patients have had a re-operation of some sort including 3.69% for stem fracture, 3.46% for neck fracture (all from a group of 95 stems with excessively machined necks), 9% for aseptic cup loosening, 3.46% for aseptic stem loosening, 1.84% for infection and 0.23% for recurrent dislocation). For the overall series, with revision for aseptic stem loosening as the end-point, the survivorship is 91.42% (95%CI: 70.82 to 100%). The average age at operation of the survivors was 57.6 years. No significant bone-cement subsidence was found. Mean stem-cement subsidence was 2.15mm, most occurring in the first 5 years and in all but 1 being less than 4mm. Cementing grades were B in 65%, C in 27%, D in 8%. Resorption of the neck (13%) was associated with excessive socket wear or cement left over the cut surface of the neck (the ‘pseudocollar’). Visible cement fractures were found in 14%, none associated with focal lysis, which was seen in 11%.

Conclusions: Although 21.7% of patients in this series of the first 433 Exeter hips to be inserted in Exeter needed a re-operation of some sort, the stem rarely required surgery for aseptic loosening and was associated with benign long-term X-Ray appearances in spite of 1st generation cementing.

Introduction We report the results of cancellous femoral impaction grafting with cement in revision hip arthroplasty in all patients from the above centre, who had their surgery more than five years previously.

Methods Up to December 1994, 226 hips underwent femoral impaction grafting in 207 patients. No deaths were attributable to the revision surgery. Thirty-three patients with 35 functioning hips died with less than five years follow-up. Only one patient was lost to follow-up. All other patients have had clinical review by two of the authors (BH and HE) and a combined panel undertook radiological review.

Results Two hips (one percent) became infected at the time of their revision surgery. Twelve stems underwent a further surgical procedure for aseptic failure; 10 for treatment of fracture and two for mechanical loosening in the absence of fracture. Survivorship with any femoral re-operation for any cause as the end point was 90.5% (confidence interval 82 to 98% (Peto equation)) at 10 to 11 years. Using femoral re-operation for symptomatic aseptic mechanical loosening as the endpoint the survivorship was 99.1% (CI= 96–100) at the same follow-up. The technique used in our centre has been modified since this series with an increased use of longer stems with impacted allograft. The technique used in Exeter has evolved and there has been an increased awareness of the fundamental importance of gaining stability of the implant within the graft at the time of surgery.

Conclusion These results provide evidence of a successful technique in the intermediate to long term.

In relation to the conduct of this study, one or more the authors have received, or are likely to receive direct material benefits.

Aims: This study reports the results of all patients from our centre who underwent femoral impaction grafting more then five years previously. As a consequence of our experience our technique has been modified and the indications for impaction grafting have become clearer. Methods: 226 hips underwent femoral impaction grafting in 207 patients. No deaths were attributable to the revision surgery. 33 patients with 35 functioning hips died with less than 5 years follow up. Only one patient was lost to follow-up. There were two (1%) acute infections. Twelve stems underwent a further surgical procedure for aseptic failure – 10 for treatment of femoral fracture and 2 for mechanical loosening in the absence of fracture. Results: Survivorship with any femoral re-operation for any cause as the end point is 90.5% (Confidence Interval 82–98%) at 10–11 years. Using femoral re-operation for symptomatic aseptic mechanical loosening as the endpoint the survivorship was 99.1% (Confidence Interval 96–100%) at the same follow-up. Conclusions: As a consequence of our experience in this series our technique has been modified with an increased use of longer stems with impacted allograft. Long stems are indicated when the host bone around a short stem is significantly compromised, in cases of severe bone stock loss, or when a fracture occurs.

The aim of this study was to determine the medium term survivorship and function of the cemented Exeter Universal Hip Replacement when used in younger patients.

Since 1988 The Exeter Hip Research Unit has prospectively gathered data on all patients who have had total hip replacements at the Princess Elizabeth Orthopaedic Hospital.

There were 88 Exeter Universal total hip replacements (THR) in 71 patients who were 50 years or younger at the time of surgery and whose surgery was performed at least 10 years before. 25 surgeons performed the surgery. Mean age at surgery was 43 years (range 24 to 50 years. ) 5 patients who had 7 THRs had died leaving 81 THRs for review. Patients were reviewed in clinic at an average of 11. 4 years (10 – 13 years). No patient was lost to follow up.

At review, 8 hips had been revised. 5 cases were for loose cemented metal backed acetabular prosthesis. Two femoral components were revised for infection and one for aseptic loosening. Radiographs showed that a further 10 (13%) acetabular prosthesis were loose and that 3 femurs showed significant osteolysis. Overall 10-year survivorship of stem and cup from all causes was 93%. The 10-year survivorship of stem only from all causes was 98% and from aseptic loosening was 99%.

The Exeter Universal Stem performs extremely well in the younger patient. However the high failure rate of the cemented metal backed Exeter acetabular component has compromised the overall results in this series.

Localised femoral endosteal bone lysis at or distal to the level of the lesser trochanter can occur soon after cemented hip arthroplasty or as long as 15 years later in a hip that has otherwise functioned perfectly well. The first important question about these lesions is why they occur, and the second, why they occur where they do. Particulate debris, particularly from wear of ultra-high molecular weight poly-ethylene, is commonly regarded as the cause, but changes in hydrostatic pressure may play a more important role than previously thought.

Because the femur bows anteriorly and posteriorly, deficiencies in the cement mantle are particularly likely to occur in relation to the interior aspect of the stem at the level of the lesser trochanter and in relation to the tip of the stem posteriorly.

We suggest that localised lytic lesions occur at the sites of defects in the cement mantle. There is evidence that with pressure changes, joint fluid and whatever particles it contains come into contact with the endosteal surface of the femur at the sites of these mantle defects. Such lesions occur only rarely when polished stems are used. With matt stems, abrasive wear enlarges the internal dimension of the cement mantle, increasing the size of the fluid conduit between stem and cement. Matt surfaced stems retrieved from patients with localised lysis show evidence of both abrasive wear and slurry wear, ‘wear caused by hard particles carried in fluid’. The nature of the changes due to slurry wear shows that the flow of fluid along these stems is from distal to proximal. As the stem becomes increasingly unstable inside the cement mantle owing to wear, the hydrostatic effects on increased stem movement become magnified and may on their own produce bone lysis.

Fundamental engineering considerations indicate that micro-movement of the components of any hip arthroplasty is inevitable: stress cannot exist without strain and vice versa. Micromovement can be classified either as inducible recoverable movement that takes place between the weight-bearing and non-weight-bearing phases of each stride, or as non-recoverable displacement between successive loading cycles.

Radiostereometric analysis is now sufficiently advanced to clarify migration and its significance, and is beginning to throw light on the extent and significance of recoverable cyclical micromovement. We discuss the value of radiostereometric analysis in identifying, early in their in-service life, implants that are likely to loosen.

The Exeter totally collarless, double-tapered femoral component was developed in 1969 jointly at the School of Engineering at the University of Exeter and the old Princess Elizabeth Orthopaedic Hospital. At the time, in common with a number of implants in contemporary use, the new Exeter stem was manufactured from the rather ductile stainless steel EN58J. The original version of the Exeter stem had a polished surface. This feature was not part of the original design specification, but was demanded by the current British standard governing the use of EN58J in orthopaedic implants. At that time, no thought was given to the possibility that the surface finish of the stem might influence outcome.

Used from 1970 to 1975, the original stems rarely came to need replacement because of loosening. The major complication was the incidence of stem fracture, first seen in 1973, which has reached 4% over a 25 to 30 year follow-up. A stronger stem was introduced at the beginning of 1976. This was manufactured from 316L. As there was no standard demanding a polished surface, this stem was manufactured with a surface two orders of magnitude rougher than the surface of the original polished Exeter stems. While the introduction of this stem almost completely solved the problem of stem fracture, with it appeared notable problems of femoral endosteal bone lysis and aseptic stem loosening, hardly seen with the original polished stems. The study of retrieved prostheses showed the matt surface stem to be prone to abrasive wear against the inside of the cement mantle, and that this phenomenon could lead both directly and indirectly to stem loosening.

Unfortunately, a decade passed before the polished stem was re-introduced in 1986. A monobloc version was used until the beginning of 1988, when the modular Exeter Universal stem was introduced. With both the monobloc and modular versions of the polished Exeter stem, both aseptic loosening and localised endosteal bone lysis have become rare.

Further retrieval studies have shown that in polished and matt Exeter stems the wear processes between stem and cement are fundamentally different. This difference may explain the substantial clinical difference in outcome between these two types of stem. These considerations lead to the view that abrasive stem wear in matt stems is probably a major cause of failure, and more important than failure of cement.